A concerted push by Nigeria's military and neighbours Chad, Cameroon and Niger has regained considerable ground in the fight against Boko Haram. The Nigerian army said it has repelled Boko Haram from all but three local government districts in the north-east.

"We have three local governments remaining, Abadam, Kala-Balge and Gwoza, and we are optimistic that with time we will liberate those," Lieutenant-General Tobiah Minimah, the army chief of staff, told reporters.

Waving captured black and white militant flags, soldiers from Niger and Chad celebrated their liberation of the Nigerian town of Damasak from Boko Haram.

The insurgents had seized Damasak with little resistance in November 2014.

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Soldiers from Niger hold up a Boko Haram flag that they seized in the town of Damasak, NigeriaEmmanuel Braun/Reuters
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A Boko Haram flag is displayed by soldiers in the recently retaken town of Damasak, NigeriaEmmanuel Braun/Reuters
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An Islamist flag flies from a mosque in Damasak, NigeriaEmmanuel Braun/Reuters
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A Boko Haram sign is seen in the recently retaken town of Damasak, NigeriaEmmanuel Braun/Reuters
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Chadian soldiers drive in the recently retaken town of Damasak, Nigeria, after armies from Nigeria, Cameroon, Chad and Niger launched an offensive to end Boko Haram's campaignEmmanuel Braun/Reuters
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Debris is scattered in front of a building that Boko Haram insurgents used as their base in Dikwa, Nigeria, before being driven out by the Chadian militaryMadjiasra Nako/Reuters
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Weapons captured from Boko Haram are seen in the recently retaken town of DamasakEmmanuel Braun/Reuters
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A man wears a sign on his back, requesting to be trained and sent to the front line to fight against Boko Haram, at a march in Yaounde, CameroonBate Felix/Reuters

Boko Haram has been fighting a six-year insurgency to create an Islamic state and had taken control of large parts of Nigeria's north-east in the past year. It became notorious internationally after kidnapping more than 200 schoolgirls last April.

At the start of this year, Boko Haram controlled around 20 local government areas, a territory the size of Belgium. In recent months, Nigeria has stepped up its campaign against the militants, and, with the help of a regional force that includes Niger and Chad, has retaken dozens of towns.

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Children fleeing from Boko Haram gather at Gudumariya Refugees Camp in NigerOlatunji Omirin/AFP
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Soldiers from Niger patrol in a truck at Kabalewa Refugee Camp, where Nigerians fleeing from Boko Haram are shelteredOlatunji Omirin/AFP

Tens of thousands of refugees fleeing Boko Haram have crossed into neighbouring Niger. Among the world's poorest countries, Niger has suffered from recurrent poor harvests, and says it will struggle to feed its people as well as the refugees.